Protective structure

ABSTRACT

A protective structure, comprising a first material region having a surface facing the exterior and an inner boundary surface, wherein channels for conducting fluid are disposed between the outer surface and the inner boundary surface, and a second material region, which is thermally connected at least in sub-regions to the inner boundary surface of the first material region and which is porous, wherein in pores a reaction medium and/or cooling medium is stored and channels for conducting fluid extend as far as the inner boundary surface of the first material region.

This application is a continuation of international application number PCT/EP2009/063237 filed on Oct. 12, 2009 and claims the benefit of German application number 10 2008 057 428.7 filed on Nov. 7, 2008.

The present disclosure relates to the subject matter disclosed in international application number PCT/EP2009/063237 of Oct. 12, 2009 and German application number 10 2008 057 428.7 of Nov. 7, 2008, which are incorporated herein by reference in their entirety and for all purposes.

BACKGROUND OF THE INVENTION

The invention relates to a protective structure.

From U.S. Pat. No. 7,281,688 B1 a heat protection system for spacecraft is known, which comprises an outer layer that is coupled to an outer support structure. This outer layer comprises a front and a back, which are connected by a connecting area. The back is in turn coupled to the outer support structure. The front, the back and the connecting area define an inner cavity, in which an ablative material is accommodated. The outer layer is of a porous design.

From U.S. Pat. No. 7,275,720 B2 a further heat protection system having a porous layer is known, wherein through the porous layer a stream of cooling fluid may flow, which is actively injected into the porous layer.

From U.S. Pat. No. 7,055,781 B2 a surface cooling device is known, comprising a porous layer that is connected to an outer structural wall and comprises a ceramic foam insulating layer. Disposed in the outer structural wall are openings, through which a stream of cooling fluid can be supplied to the porous layer.

From U.S. Pat. No. 2,908,455 a vehicle is known, which comprises a pair of mutually spaced layers of a structural material, wherein an outer layer is porous and is exposed to an air stream, an absorbent filling material is disposed between the layers, means for conducting heat through the filling material are provided, means for distributing a cooling medium exist in the filling material, and the cooling medium is capable of absorbing large quantities of heat during evaporation.

From WO 03/006883 A1 a coolable segment for a turbine-type machine is known, wherein the turbine-type machine is operated by means of a hot fluid. The segment comprises a cooling wall that extends in an axial direction and in a peripheral direction orthogonal to the axial direction a hot fluid surface is provided, which is exposed to the hot fluid. Situated between the cooling wall and the hot fluid surface is a cooling structure, which is permeable to cooling fluid and provides cooling surfaces for cooling through heat transfer by means of radiation.

From EP 1 641 959 B1 a layered structure is known, which consists of a substrate and an at least partially porous, partially gas-permeable layer on the substrate, wherein the substrate has cooling channels, through which a cooling medium may pass through the substrate into the porous layer. The porous layer has pores that are delimited by walls, wherein on the walls there is at least partially a coating.

From U.S. Pat. No. 3,825,364 a turbo-type machine is known, which has outer and inner layers of a porous material.

From U.S. Pat. No. 2,941,759 an aeronautical heat exchanger is known.

SUMMARY OF THE INVENTION

In accordance with the present invention, a protective structure that is self-activating and exhibits high protection properties is provided.

In accordance with an embodiment of the present invention, the protective structure comprises a first material region having a surface facing the exterior and an inner boundary surface, wherein channels for conducting fluid are disposed between the outer surface and the inner boundary surface, and a second material region, which is thermally connected at least in sub-regions to the inner boundary surface of the first material region and which is porous, wherein in pores a reaction medium and/or cooling medium is stored and channels for conducting fluid extend as far as the inner boundary surface of the first material region.

By virtue of the solution according to the invention an active protective structure is provided, which in an “emergency” provides a reaction medium and/or cooling medium, wherein this provision is possible by means of an in particular thermal and/or chemical self-activation (without external triggering). The protective structure itself is in this case of a passive design; the reaction medium and/or cooling medium is stored in the protective structure itself.

The protective structure in a deployment situation retains its contour, i.e. it is geometrically stable. This means that for example the aerodynamic properties of a missile (if for example the protective structure is configured as a heat protection system during entry into the atmosphere) are not negatively influenced by excessive removal of material.

By means of the thermal connection between the first material region and the second material region provision is made for heat conduction. It is therefore possible to transfer enough heat into the second material region for the heat transfer to be no longer purely produced by radiation. This means for example that a cooling medium is able to complete one or more phase changes more rapidly. In this way, for example in the case of transpiration cooling and/or effusion cooling greater efficiency may be achieved.

In order for example to cater for a phase change of a cooling medium for transpiration cooling and/or effusion cooling, in the solution according to the invention lower temperatures are required at the first material region.

In the second material region in principle any possible form of reaction medium and/or cooling medium may be stored. Solid, gaseous, liquid reaction media and/or cooling media or alternatively reaction media and/or cooling media in gel form may be stored.

In principle it is also possible to store a reaction medium that, when it escapes to the surface, is capable of neutralizing a chemically aggressive substance. Optionally, in this case locally contaminated places at the surface may be agglutinated and sealed.

In principle cooling medium and/or reaction medium may also be stored in the first material region.

It is particularly advantageous if the first material region is manufactured from a material that in the event of corresponding thermal stress or chemical attack exhibits a high stability under load. For example, for applications involving thermal stress the first material region is manufactured from a material that has a high thermal conductivity and preferably also a high emissivity. It is thereby ensured that this material is able to withstand high temperatures. This in turn makes it possible to keep the proportion of subsequently activated cooling medium low.

In a corresponding manner it is advantageous if in the event of chemical attack the first material region has a high resistance to potential reaction media.

In principle, the protective structure according to the invention is also re-usable in that the first material region and/or the second material region is “refilled”, i.e. cooling medium and/or reaction medium after “emptying” is replenished.

The solution according to the invention may be realized for example in the configuration as a heat protection system also in conjunction with lightweight construction concepts, because an increased cooling efficiency enables thinner structures (for the protective structure and the elements that are to be protected).

It is advantageous if the first material region or the second material region are of an open-pored design. In this way, channels are provided for conveying reaction medium and/or cooling medium from the second material region to the inner boundary surface of the first material region and for conveying reaction medium and/or cooling medium from this inner boundary surface to the surface.

In this case it is in principle advantageous if the second material region has a higher porosity than the first material region. The pores in the second material region are used to store cooling medium and/or reaction medium. By virtue of a greater porosity a large quantity of reaction medium and/or cooling medium can be stored.

In principle it is also possible for the first material region and/or the second material region to have channels formed by cracks and/or bores to enable the conveying of fluid.

In an advantageous embodiment a layer of activating medium is disposed on the surface of the first material region facing the exterior and/or the channels of the first material region are infiltrated with activating medium, wherein the activating medium closes the channels leading to the exterior and wherein the activating medium may be activated thermally and/or chemically in order to open the channels in the direction of the exterior. The activating medium closes the channels to prevent the reaction medium and/or cooling medium from escaping in the undeployed situation. If the reaction medium and/or cooling medium is for example under pressure, it may escape through the first material region. This is prevented by the activating medium. By infiltrating the channels it is also possible to achieve a greater stability under load if the reaction medium and/or cooling medium is loaded with overpressure. The activating medium effects a sealing in the first material region. In this case it is in principle possible for the channels to be infiltrated with activating medium only partially along a channel direction, or for the channels to be completely infiltrated with activating medium.

If no additional outer layer of activating medium is provided, then upon activation and decomposition of the activating medium the surface and/or the contour of the protective structure is also at most minimally influenced. This may be advantageous for example in the case of missile applications.

It is however also possible that in addition or as an alternative to the infiltration of the channels a layer of activating medium is disposed on the surface. This may for example be advantageous if the first material region is of an open-pored design in order to obtain a smooth surface. Such a smooth surface may be desired for aesthetic reasons or may be advantageous for specific applications.

The activating of the activating medium may be effected for example thermally. The activating medium may in this case decompose or melt open and hence release the channels. A chemical activation is in principle also possible. In the case of chemical activation, the activating medium reacts with a reactant introduced from outside and unblocks the channels so that reaction medium and/or cooling medium may in turn be released from the second material region.

In principle it is possible for the second material region to be fluidically connected to a reservoir device for reaction medium and/or cooling medium. This allows an additional supply of reaction medium and/or cooling medium.

For example, it is thereby also possible to apply pressure to the reaction medium and/or cooling medium in order to provide an overpressure that drives reaction medium and/or cooling medium from the second material region into the first material region.

In one embodiment the reservoir device is formed by a third material region or comprises such a third material region. The third material region is in particular connected over its entire surface to the second material region in order to enable an additional supply of reaction medium and/or cooling medium to the second material region over a high surface area.

In an advantageous manner a support structure is provided, to which the combination of first material region and second material region is fastened. The support structure itself is fastened to an application or part of the application.

The reaction medium and/or cooling medium that is stored in the second material region may be stored in the form of a gas, a solid or a liquid or it may be stored as a gel. In the solution according to the invention various states of aggregation are possible in principle.

In particular reaction medium and/or cooling medium may be conveyed by capillary action and/or by overpressure of the reaction medium and/or cooling medium from the second material region to the surface of the first material region. It is thereby possible to achieve in particular an automatic conveying to the surface upon activation of the protective structure.

In principle it is possible for the first material region and/or the second material region to be configured with homogeneous material properties. It is however also possible for the material properties to be graduated, i.e. for the material properties to vary in one or more directions and in particular for a variable porosity to be set.

In this case it may be provided that the first material region and the second material region are formed integrally to one another. The reaction medium and/or cooling medium is stored in the second material region. The corresponding structure is filled with reaction medium and/or cooling medium to a specific depth below the outer surface.

It is alternatively possible for the first material region and the second material region to be manufactured by separate material layers.

In an advantageous embodiment a heat-insulating layer is disposed between the first material layer and the second material. The heat-insulating layer ensures that the second material region is not heated to such an extreme extent and high temperatures are confined substantially to the first material region. A temperature reduction is achieved relative to the second material region.

In particular the heat-insulating layer is multiply connected, i.e. it has mutually spaced “holes”. Through these holes in turn the introduction of a heat flow from the first material region into the second material region is possible.

In an advantageous manner the first material region and the second material region are thermally connected in the region of holes of the heat-insulating element. This allows heat from the first material region and hence from the exterior to be introduced in the second material region in order to achieve for example rapid phase changes and hence, in the case of transpiration cooling and/or effusion cooling, efficient cooling.

In particular, at holes of the insulating layer strips project from the first material region into the second material region. The strips in this case in particular completely fill the holes and are surrounded by the material of the second material region and form an inner boundary surface adjacent to the second material region. This effectively allows heat to be injected into the second material region.

In this case it may be provided that strips project as far as a support structure for the second material region or as far as a third material region, on which the second material region is disposed. Effective support is thereby achieved, with the result that the protective structure has a high mechanical stability.

It may be provided that strips are configured in the shape of a cuboid and/or pyramid and/or truncated pyramid and/or cone and/or truncated cone and/or wedge and/or truncated wedge and/or cylinder. In this way it is possible to provide a large surface, which is an inner boundary surface relative to the second material region. This in turn leads to an effective introduction of heat into the second material region.

It is quite particularly advantageous if the strips are manufactured from the material of the first material region. In particular, they are integrally (cohesively) connected to the first material region. This results in an effective introduction of heat.

In one embodiment the first material region (and/or the second material region) is manufactured from a fibre material or fibre-ceramic material or ceramic material. Such a material may be of an open-pored design. The material for the first material region is for example a carbon-based fibre ceramic with or without carbon fibres or an oxide-ceramic fibre ceramic or a sintered ceramic. Other materials are also possible, such as for example metal, open-pored (hollow) sphere packings or open-pored sintered metals.

For example the first material region is manufactured from graphite or C/C or SiC or C—SiC or C/C—SiC.

The cooling medium is preferably selected in such a way that transpiration cooling and/or effusion cooling occurs. In the case of transpiration cooling and/or effusion cooling, convective cooling is effected as a result of the cooling medium flowing out. A thermal block boundary layer develops at the outside of the protective structure and a reduction of the occurring heat flow is achieved. By additional absorption of the fusion- and evaporation enthalpy the cooling effect is improved.

The protective structure according to the invention may be used for example as a heat protection system for a missile or for a combustion chamber or for a furnace or for fire protection of a building or for a reactor.

It is also possible to use the protective structure according to the invention in the neutralizing of chemical substances, wherein as a reaction medium a reactant for a chemical substance attacking the protective structure is selected. In the event of a corresponding attack, in particular after chemical activation of an activating medium the reaction medium may escape and react with the aggressive chemical substance and neutralize it. Given a suitable choice of the reaction medium, the effect may be achieved whereby the reaction product that arises agglutinates contaminated points of the surface and for example a sealing is also effected.

The following description of preferred embodiments serves in conjunction with the drawings to provide a detailed explanation of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a diagrammatic representation of a sub-region of a protective structure according to the invention;

FIG. 2 shows a diagrammatic representation of a sub-region of a second embodiment of a protective structure according to the invention;

FIG. 3 shows a perspective partial representation of a third embodiment of a protective structure according to the invention;

FIG. 4 shows a sectional view of the protective structure according to FIG. 3; and

FIG. 5 shows a view similar to FIG. 4 with an alternative strip configuration.

DETAILED DESCRIPTION OF THE INVENTION

A first embodiment of a protective structure according to the invention, which is shown diagrammatically in a partial view in FIG. 1 and denoted there by 10, is disposed on an element 12 that is to be protected. Corresponding application examples are described below. The protective structure 10 comprises a support structure 14 that is fastened to the element 12 to be protected. For example, the support structure 14 is adhered or connected in some other way to the element 12 to be protected. In principle, it is possible in this case for the element 12 to be protected and the support structure 14 to be of an integral construction.

The support structure 14 carries a first material region 16 and a second material region 18. The first material region 16 is an outer material region, which has a surface 20 facing the exterior 22.

The first material region 16 has an inner boundary surface 24 relative to the second material region 18. The second material region 18 and the first material region 16 are connected to one another by the inner boundary surface 24, wherein a thermal contact is established. In the protective structure 10 a full-surface contact between the first material region 16 and the second material region 18 is therefore provided at the inner boundary surface 24, with the result that a full-surface thermal contact is also established.

Embodiments, in which the thermal contact is established only in sub-regions, are additionally described further below.

Disposed in the first material region 16 are channels 26, which are used to conduct fluid and extend from and in particular as far as the inner boundary surface 24 to the surface 20. In FIG. 1 the channels 26 are indicated diagrammatically in the detail enlargement A.

The channels are used to conduct fluid through the first material region 16 to the surface 20. The corresponding fluid may in this case be used as a cooling medium in order in particular to realize transpiration cooling and/or effusion cooling. It is in principle also possible for the corresponding fluid to be a reaction medium, which is used for example as a reactant in order to neutralize a medium that is attacking the protective structure 10. This is described in greater detail further below.

The channels 26 may be realized in different ways. They may be manufactured for example “macroscopically”, such as for example by means of bores. They may be manufactured “microscopically” by means of cracks in the first material region 16. The first material region 16 may be of an open-pored design and in this way a channel structure may be formed in the first material region 16. Combinations of different channel configurations are also possible.

The second material region 18 is a reservoir area. It is of a porous design having pores 28 (detail enlargement B in FIG. 1), in which reaction medium and/or cooling medium 30 is stored. Formed in the second material region 18 are channels 32, through which reaction medium and/or cooling medium 30 may pass to the inner boundary surface 24 and, from there, to the surface 20. The channels 32 are formed for example by an open-pored structure, in which the pores 28 are connected to one another. In principle the channels 32 may also be produced for example by cracks or the like.

The second material region 18 has a lower density than the first material region 16 (wherein the filling of the pores 28 with reaction medium and/or cooling medium 30 in the second material region 18 is not taken into consideration when determining the density, i.e. the pores 28 are regarded as “empty pores). If the first material region 16 is of a porous design, then the second material region 18 has a higher porosity than the first material region 16, i.e. the relative proportion of pores in the second material region 18 is greater than in the first material region 16.

It is possible for the second material region 18 to be connected to a reservoir device 34, which effects a subsequent supply of reaction medium and/or cooling medium, wherein this reaction medium and/or cooling medium is for example under pressure.

Depending on the application, the reaction medium and/or cooling medium 30 may be stored in the second material region 18 in the form of a solid, a gas or a liquid or as a gel. If the reaction medium and/or cooling medium 30 is stored in non-fluid form (i.e. in non-flowable form) and is stored for example as a solid (for example in powder form or solid material form), then the transformation to a flowable material is possible in particular by means of thermal loading from the direction of the first material region 16.

In a variant of an embodiment the channels 26 in the first material region 16 are closed in the direction of the surface 20 by means of an activating medium 36. This prevents reaction medium and/or cooling medium 30 from being able to escape through the channels 26 when a protective deployment situation of the protective structure 10 does not exist. The activating medium 36 infiltrates the channels 32, as is denoted in FIG. 1, detail view A by the reference character 38.

In principle, a layer 40 of activating medium 36 may be disposed on the surface 20 of the first material region 16. This layer 40 need not necessarily be continuous. For example, the layer 40 is used to produce a uniform and in particular smooth surface on the first material region 16, if the first material region 16 is of a porous design. This may for example, independently of technical specifications, also be a requirement for aesthetic reasons in specific applications.

The activating medium 36 may be activated thermally and/or chemically. In the case of thermal activation, the activating medium 36 decomposes above a specific temperature threshold. As a result, the channels 26 are opened in the direction of the surface 20 and reaction medium and/or cooling medium 30 may escape.

In the case of chemical activation, the activating medium 36 reacts with a reactant applied from the outside (via the exterior 22) and decomposes in order, in the manner described above, to release the channels 26 and in turn allow reaction medium and/or cooling medium 30 to escape.

The conveying of reaction medium and/or cooling medium 30 through the channels 26 in the first material region 16, including the conveying towards the first material region 16, is driven by capillary forces and/or by loading the reaction medium and/or cooling medium in the second material region 18 with pressure.

The protective structure 10 operates as follows:

The protective structure 10 is used for example as a heat protection structure for the element 12. In this case, the stored medium is a cooling medium and the activating medium 36 is thermally activated.

The protective structure 10 is disposed on the element 12. If this system is exposed to “too high” a temperature, i.e. one that lies above a temperature threshold, the activating medium 36 is activated. The sealing of the first material region 16 is terminated as a result of decomposition of the activating medium 36 and the channels 26 are unblocked. Cooling medium 30, which is stored in the second material region 18, may then pass from the second material region 18 through the first material region 16 to the surface 20. A subsequent supply of cooling medium 30 to the second material region 18 may optionally occur by means of the reservoir medium 34.

After activation of the activating medium 36, cooling medium may flow through the first material region 16. Via thermal activation of the activating medium 36, which is in particular a melting or sublimation, fluid paths through the first material region 16 to the surface 20 are unblocked. A flow is likewise possible through the second material region 18 in order to be able to supply cooling medium to the first material region 16.

The flow through the second material region 18 and the first material region 16 is driven by capillary forces and/or overpressure of the cooling medium.

It is possible to achieve a transpiration cooling and/or effusion cooling, which is achieved for example by phase changes of the cooling medium. A convective cooling of the protective structure 10 occurs, wherein a thermal block boundary layer may develop from the cooling medium at the surface 20 of the first material region 16. The heat flow that arises and leads in principle to heating of the element 12 is therefore reduced.

In principle the cooling effect through use of a liquid or solid cooling medium may be improved by additional absorption of the enthalpy of fusion and evaporation.

The first material region 16 is thermally coupled to the second material region 18. The pores 28 are surrounded by solid material of the second material region 18. This results in an optimized injection of heat; heat may be effectively coupled in from the surface 20 into the second material region 18. As a result, compared to heating caused purely by radiation, more heat is supplied to the cooling medium. The cooling medium may therefore complete one or two phase changes more rapidly; this in turn increases the cooling efficiency.

Compared to a heat exchange caused purely by radiation, the heat introduction needed in the solution according to the invention for a phase change of the cooling medium is achievable by lower temperatures of the first material region 16.

In this case it is in principle possible for the cooling medium 30 to be stored in the second material region 18 not only in solid form (for example powder form). In principle it is also possible for it to be stored in liquid form or as a gel or alternatively as a gas.

In this case it is in principle possible for the first material region 15 and the second material region 18 to be integrally connected to one another and in particular to be made of the same material, which is differently configured. For example, this material then has a lower porosity in the first material region 16 than in the second material region 18. In this sense the first material region 16 and the second material region 18 in their combination are then configured as one layer.

It is however also possible for the first material region 16 and the second material region 18 to be separate layers.

In principle, it is such that in the first material region 16 no cooling medium is stored.

Selection of the material for the activating medium 36, the material for the first material region 16 and the material for the second material region 18 is determined by the application.

The first material region 16 is manufactured for example from a porous fibre-ceramic material such as C/C or from graphite. In this case the fibres may, depending on the application, lie parallel or perpendicular or in other orientations relative to the surface 20. The first material region 16 may also be manufactured from other carbon-based fibre ceramics such as SiC, C—SiC, C/C—SiC etc. It may be manufactured from sintered ceramic materials or oxide ceramic fibre-ceramic materials. It may for example also be manufactured from metal, open-pored (hollow) sphere packings or from open-pored sintered metals.

Depending on the application, the activating medium is for example a wax, an epoxy resin or a lacquer. Other types of activating medium are also possible.

The second material region 18 is manufactured from a highly porous material such as for example C/C. (In a material such as C/C the porosity is in principle easy to adjust.) Other materials are also possible, such as for example high-temperature insulating materials used in furnace construction. Examples of these are carbon-fibre nonwoven fabrics, aluminium oxide materials or carbon felt nonwoven fabrics.

The reaction medium and/or cooling medium is selected in dependence upon the application. Possible media are for example water, a primary material, wax, Teflon, inert cooling gases etc.

The protective structure 10 is usable also in the event of chemical attack. In this case, a reaction medium 30 is stored in the second material region 18. The reaction medium 30 is selected in such a way that, when it reaches the surface 20, it may react with a chemical substance acting upon the protective structure 10 and may neutralize this chemical substance.

In this situation, if an activating medium 36 is used, with which the channels 26 are infiltrated, the chemical activating medium may be activated chemically. It decomposes under the action of the chemical substance, so that the channels 26 are unblocked. The reaction medium 30 may then flow to the surface 20 and come into contact with the chemical substance that is attacking the protective structure 10 from the outside. By means of the reaction undesirable chemical states of this attacking medium are eliminated. For example, the attacking chemical substance is an aggressive acid-containing substance, which is chemically neutralized by the reaction medium 30.

In this case it is possible for the reaction medium to combine with the attacking substance and for this compound to “eliminate” locally contaminated points at the surface 12 in that for example an agglutination and a type of sealing occurs at the surface 20.

The reaction medium 30 is then selected in accordance with the attacking medium in order to achieve a neutralization.

In this case too, further reaction medium 30 can be provided to the second material region 18 by means of the reservoir device 34. This additional conveying of reaction medium 30 is optionally effected mechanically.

In FIG. 1 this additional conveying is indicated by the arrow having the reference character 42. The arrow having the reference character 44 indicates the flow of reaction medium and/or cooling medium 30 from the second material region 18 through the first material region 16 to the surface 20.

The channels 26 are infiltrated by the activating medium 36. In principle a layer 40 is not needed to achieve closure of the channels 26. Consequently, upon decomposition of the activating medium 36 no change in the geometry of the combination of element 12 and protective structure 10 arises; the contour is retained. Infiltration of the channels 26 results in a greater stability under pressure, if pressure is applied to the reaction medium and/or cooling medium 30.

In principle, no activating medium 36 need be provided for closing the channels 26 if the reaction medium and/or cooling medium 30 stored in the second material region 18 does not flow automatically and in particular without thermal loading above a specific temperature threshold into the first material region 16.

If for example the reaction medium and/or cooling medium 30 is stored in the second material region 18 in solid form (for example in powder form) or in gel- or liquid form and, before it can flow out of the pores 28 and into the first material region 16, a “thermal activation” is required in order for example to melt open the reaction medium and/or cooling medium 30 and/or lower the viscosity or the like, then it is possible to dispense with an infiltration of the channels 26 with activatable activating medium 36.

A second embodiment of a protective structure according to the invention, which is shown diagrammatically in FIG. 2 and designated there by 46, is basically similar in construction to the protective structure 10. A first material region 16′ is provided, which lies above a second material region 18′. The first material region 16′ faces the exterior 22. The first material region 16′ is in principle identical in construction to the first material region 16 and the second material region 18′ is in principle identical in construction to the second material region 18 of the protective structure 10 and they have the same tasks.

The second material region 18′ is however not disposed directly on a support structure 14′, rather a third material region 48 is disposed between the support structure 14′ and the second material region 18′. This third material region 48 is in particular of a porous design and is an additional reservoir area. It has channels that lead to the second material region 18′. The third material region 48 may be fluidically connected to a reservoir device 50. In the third material region 48 reaction medium and/or cooling medium 30 may additionally be stored, which may then be supplied via an inner boundary surface 52 to the second material region 18′. In particular, a two-dimensional connection is provided between the second material region 18′ and the third material region 48.

A greater flow of reaction medium and/or cooling medium may therefore be supplied to the first material region 16′. The proportion of stored cooling medium in the protective structure 46 is increased compared to the protective structure 10 and/or the supply of reaction medium and/or cooling medium to the second material region 18′ may be increased because the entire third material region 48 is provided as a distributor.

An additional conveying of reaction medium and/or cooling medium may be effected for example mechanically by means of the reservoir device 50. The third material region 48 itself forms a reservoir device for the second material region 18′.

Otherwise the protective structure 46 operates like the protective structure 10.

A third embodiment of a protective structure according to the invention, which is shown in FIGS. 3 to 5 and denoted there by 54, comprises a first material region 56 that faces the exterior 22. A second material region 58 is provided. The first material region 56 corresponds to the first material region 16 of the protective structure 10. In it channels corresponding to the channels 26 are disposed for conducting fluid. Through these channels reaction medium and/or cooling medium may be brought to a surface 60. The channels may in this case be sealed with activating medium corresponding to the activating medium 36.

The second material region 58 is a reservoir area corresponding to the second material region 18 of the protective structure 10. In corresponding pores 28 reaction medium and/or cooling medium 30 is stored. The second material region 58 is seated on a support structure 62 corresponding to the support structure 14. In this case it is possible for a third material region corresponding to the third material region 48 to be provided between the support structure 62 and the second material region 58.

On the first material region 56 a heat-insulating layer 64 facing the second material region 58 is disposed. This heat-insulating layer 64 in sub-regions separates the first material region 56 from the second material region 58. The heat-insulating layer 64 is manufactured from an appropriate insulating material such as for example a ceramic material or an oxide material or the like.

The heat-insulating layer 64 is multiply connected. It has “holes” 66, wherein these holes 66 are spaced apart from one another. Disposed in each case at these holes 66 are strips 68, which are manufactured from the material of the first material region 56 and engage through the holes 66 in the heat-insulating layer 64 and project into the second material region 58.

These strips 68 represent thermal bridges, via which heat may be introduced from the first material region 56 into the second material region 58. A thermal coupling between the first material region 56 and the second material region 58 is therefore achieved, by means of which reaction medium and/or cooling medium 30 in the second material region 58 may be heated.

The strips 68 may in this case be spaced apart from a boundary layer 70 of the second material region 58 or reach as far as this boundary layer 70 (FIGS. 4 and 5) and be positioned for example on the support structure 62 and/or the third material region in order to achieve greater stability and to increase the area of heat transfer into the second material region 58.

The strips 68 may be configured for example in the shape of a truncated wedge or a cylinder or a truncated pyramid (FIG. 4) or in the shape of a cuboid (FIG. 5).

It is also possible for the heat-insulating layer 64 to have strips 72, via which it is supported on the support structure 62 and/or the third material region (FIG. 3).

The strips 68 are elements of the first material region 56 that are surrounded by the material of the second material region 58 for the purpose of heat introduction. The strips 68 in this case have channels to enable the conveying of reaction medium and/or cooling medium 30 to the surface 60. The heat-insulating layer 64 may likewise have channels to enable the conveying of reaction medium and/or cooling medium through to the first material region 56 and, from there, to the surface 60.

The heat-insulating layer 64 is used to adjust the temperature gradient at the protective structure 54. In principle, it is such that high temperatures are desired only in the first material region 56. The heat-insulating layer 64 brings about a considerable temperature reduction; there is a (partial) thermal decoupling of the second material region 58 from the first material region 56. The necessary introduction of heat into the second material region 68 is effected by means of the strips 68, so that provision is made for an adequate transfer of heat from the first material region 56 to the second material region 58 and this heat transfer is not exclusively radiation-conditioned.

The strips 68 and the strips 72 may also help to increase the mechanical stability of the protective structure 54.

The first material region 56 has two types of inner boundary surface, namely an inner boundary surface 74 facing the heat-insulating layer 64 and an inner boundary layer 76 formed on the strips 68 that is a boundary layer relative to the second material region 58. The corresponding channels leading to the surface 20 may extend from the inner boundary surface 74 to the surface 60 and/or from the inner boundary surface 76 to the surface 60.

Otherwise the protective structure 54 operates like the protective structures 10 and 46.

The protective structures according to the invention may be used in different fields. For example, with a protective structure according to the invention a heat protection system may be realized. Such a heat protection system in turn has various applications such as for example aerospace applications.

In particular, the protective structure according to the invention is in principle refillable, i.e. cooling medium and/or reaction medium may be re-stored in the second material region so that, even after achieving the protective effect of the protective structure, recycling is possible.

For example, upon re-entry of a missile into the atmosphere a corresponding element 12 of the missile upon reaching corresponding temperatures may be cooled in a contour-stable manner, wherein in particular transpiration cooling and/or effusion cooling is used. In this case it is possible also to achieve a protective effect for only a limited period of time (if no additional conveying of cooling medium into the second material region is effected).

It is possible for example also to cool drive components or a combustion chamber for example of a rocket. For example, the protective structure serves as a single-use, exchangeable segment, which during launching of a rocket at appropriate temperatures brings about a cooling process.

A protective structure according to the invention may be used for example also in furnace construction. In the event of thermal overload of the furnace, cooling is achieved by means of self-activation.

The solution according to the invention may be used for example also as protection and in particular fire protection of structures such as buildings and tunnels. For example, walls such as tunnel walls may be composed of segments. A water supply may be provided inside a corresponding segment structure. A reservoir device 34 is consequently provided. In the event of fire, a self-activation of the protective structure according to the invention occurs. This brings about a water-cooling of the walls with a reduction of the prevailing temperatures.

It is for example also possible for a reactor such as a chemical reactor or a nuclear reactor to be cooled in the event of thermal overload by means of a protective structure according to the invention in a self-activating manner.

For chemical applications such as for example in the chemical industry, petroleum industry or in process management systems, a neutralization or sealing may be carried out in the manner described above, if an appropriate reaction medium 30 is used.

The protective structure according to the invention is self-activating. In the event of a temperature threshold being exceeded and/or a corresponding attacking medium being effective, the release of reaction medium and/or cooling medium 30 to the surface may be activated. The protective structure 10 itself may be of a basically passive design. The reaction medium and/or cooling medium 30 is stored in the second material region 18 and/or 18′ and/or 58 and is therefore held at least temporarily in readiness. 

1. Protective structure, comprising: a first material region having a surface facing the exterior and an inner boundary surface; channels for conducting fluid being disposed between the outer surface facing the exterior and the inner boundary surface; and a second material region, which is thermally connected at least in sub-regions to the inner boundary surface of the first material region and which is porous; wherein in pores at least one of a reaction medium and a cooling medium is stored; and wherein channels for conducting fluid extend as far as the inner boundary surface of the first material region.
 2. Protective structure according to claim 1, wherein at least one of the first material region and the second material region is of an open-pored configuration.
 3. Protective structure according to claim 2, wherein the second material region has a higher porosity than the first material region.
 4. Protective structure according to claim 1, wherein at least one of the first material region and the second material region has channels formed by at least one of cracks and bores.
 5. Protective structure according to claim 1, wherein at least one of (i) a layer of activating medium is disposed on the surface facing the exterior; and (ii) the channels of the first material region are infiltrated with activating medium, wherein the activating medium closes the channels leading to the exterior and wherein the activating medium is adapted to be activated at least one of thermally and chemically in order to open the channels in the direction of the exterior, is provided.
 6. Protective structure according to claim 1, wherein the second material region is fluidically connected to a reservoir device for at least one of reaction medium and cooling medium.
 7. Protective structure according to claim 1, wherein the reservoir device is formed by a third material region or comprises such a material region.
 8. Protective structure according to claim 1, said protective structure comprising a support structure, to which the combination of first material region and second material region is fastened.
 9. Protective structure according to claim 1, wherein at least one of the reaction medium and the cooling medium is stored in the second material region in the form of a gas, a solid or a liquid or as a gel.
 10. Protective structure according to claim 9, wherein at least one of the reaction medium and the cooling medium is conveyable by at least one of capillary action and overpressure of at least one of the reaction medium and the cooling medium from the second material region to the surface of the first material region.
 11. Protective structure according to claim 1, wherein the first material region and the second material region are integrally connected.
 12. Protective structure according to claim 1, wherein the first material region and the second material region are manufactured by separate material layers.
 13. Protective structure according to claim 1, wherein a heat-insulating layer is disposed between the first material region and the second material region.
 14. Protective structure according to claim 13, wherein the heat-insulating layer is multiply connected.
 15. Protective structure according to claim 14, wherein in the region of holes of the heat-insulating layer the first material region and the second material region are thermally connected.
 16. Protective structure according to claim 15, wherein at holes of the heat-insulating layer strips project from the first material region into the second material region.
 17. Protective structure according to claim 16, wherein strips project as far as a support structure for the second material region.
 18. Protective structure according to claim 16, wherein strips are configured in the shape of at least one of (i) a cuboid; (ii) pyramid; (iii) truncated pyramid; (iv) cone; (v) truncated cone; (vi) wedge; (vii) truncated wedge; (viii) cylinder.
 19. Protective structure according to claim 16, wherein the strips are manufactured from the material of the first material region.
 20. Protective structure according to claim 1, wherein the first material region is manufactured from a fibre material or fibre-ceramic material or ceramic material.
 21. Protective structure according to claim 20, wherein the first material region is manufactured from graphite or C/C or SiC or C—SiC or C/C—SiC.
 22. Protective structure according to claim 1, wherein the cooling medium is selected so that at least one of transpiration cooling and effusion cooling is effected. 